The present invention relates to a drum brake wherein a fitting construction of a wheel cylinder device is simplified so as to lighten the weight of a brake and facilitate disassembly and assembly of the brake, and further provide a function of a duo-servo brake.
In the conventional brakes of the kind, a wheel cylinder has been provided with flanges through which fitting bolts are inserted in order to fit the wheel cylinder to a backing plate. Therefore, it has been found that these assemblies suffer from the shortcoming of excessive weight formed by a volume of the cylinder body relative to the fitting portions such as flanges and the fitting bolts.
The present invention is directed to solve the shortcoming and has obtained an expected result in an arrangement wherein a piston of a wheel cylinder operating to expand brake shoes of a drum brake is slidably engaged through an anchor provided on a backing plate.
Further, the drum brake of the present invention provides a duo-servo function when the wheel cylinder is located between a pair of adjacent shoe ends for a pair of brake shoes and a strut is located between the other pair of adjacent shoe ends for the pair of brake shoes. In this case, the piston is provided with a flange on the side thereof pressing a brake shoe and the anchor aforementioned is advantageously interposed between the flange and the wheel cylinder.
In other words, it is because the wheel cylinder device is not only slidably supported by the anchor of the backing plate but also the flange of the piston or the wheel cylinder abuts on the anchor according to a rotating direction of a drum caused by a rotating force of the drum during a braking operation.
The drum brake of the present invention simplifies a fitting construction of the wheel cylinder device without impairing a function of a drum brake, lightens the weight of the brake, facilitates disassembly and assembly of the brake and functions as a duo-servo brake in such an arrangement as mentioned above.
Furthermore, if the anchor is integrated with the backing plate, the anchor becomes favorable in a strength in addition to the foregoing advantage.